Hi there Joe. I just bought and received one of these nifty dbx 21 units - NOS.
I am trying to figure out what Input I am supposed to run my Primaluna EVO 100 Phono Preamp into it, and then what Output I am supposed to come out of to send to an AUX Input on my Primaluna Dialogue Premium Integrated Amplifier for playing back dbx Encoded records.
I am sure by now that you have obtained a copy of the Owner's Manual for the dbx 21 but if not, here is a link to Vinyl Engine to download a copy https://www.vinylengine.com/library/dbx/21.shtml.
Let me know if you figured out how to install a Phono Preamp into the equation for playing back records! Thanks - Dana